Ethanolamine hydrochloride softener for regenerated cellulose



Patented Sept. 24, 1940 UNITED STATES PATENT OFFICE ETHANOLAMINE HYDROCHLORIDE SOF- TENEB FOB REGENERATED CELLULOSE Franklin Traviss Peters, Wilmington, DeL, as-

signor to E. I. du Pont de Nemours &

Company,

Wilmington, Del., a corporation of Delaware No Drawing. Application May 9, 1939, I Serial No. 272,641

9 Claims. (01. 106-40) ,ing the same with softening agents, and the products resulting from such treatment.

In the manufacture of cellulosic pellicles of 'the type precipitated from aqueous alkaline cellulosic solutions, such as regenerated cellulose 10 pellicles, including sheets or films, caps, bands,

continuous tubing, artificial straw andthe like, it has long been customary to incorporate into the cellulosic pellicle a softening agent in order to maintain it in a flexible condition. Such cel- '15 lulosic pellicles, when free from a softening agent, are known to be quite brittle, and while a softener free pellicle may find certain uses, a softened and therefore flexible sheet or film is much more generally useful. Heretofore, as

softeners for regenerated cellulose, and similar water sensitive, cellulosic pellicles, the art has applied such substances? as ethylene glycol, pro- 7 pylene glycol, diethylene glycol, formamide, glycerol, and the like, but of these, by far the \most important is glycerol which has hitherto known noequal as a softening agent of general utility for producing flexible, transparent and durable, water sensitive, cellulosic pellicles such as those of regenerated cellulose. Many attempts have been made to find a softener for water sensitive, cellulosic "pellicles which will be as cheap asand which will have the generally useful softening characteristics of glycerol. After continued use .of previously discovered softening agents, they were found to be deficient in some respect and therefore could not be generally substituted for glycerol as a softening agent for regenerated cellulose and like water sensitive, cellulosic pellicles.

. 4o Glycerol is obtained commercially primarily as a by-product from the soap industry. As a bya product, the quantity may be limited and hence glycerol is subject to market fluctuations of supply as well as price. Glycerol has been particu 45 larly high. priced and diflicultly obtainable during periods of war when large quantities are used in the production of munitions. The glycols, mentioned above as useful cellulose softeners, are for the most part obtained by a relatively expensive o process of synthesis. The glycols are also relatively volatile and are therefore unsatisfactory for use in softening some types of cellulosic pellicles. For an industry consuming large amounts of these materials, therefore, the devel- 55 opment of less expensive equivalents or means for reducing the consumption of expensive-materials will mean a marked economy in production.

It is, therefore, an object of this invention to provide a new and useful method for producing 5 softened, water sensitive, cellulosic materials possessing desirable physicalproperties. It is a further object of this invention to provide water sensitive, cellulosic materials having a softening agent associated therewith, which softening l0 agent will not interfere with any subsequent treatment of the cellulosic pellicles, such as the application of surface coatings, ink, coloring matter, adhesives, or the like. It is a still further object of this invention. to provide a. rigid, l5 flexible, transparent, durable, cellulosic pellicl such as a sheet, film, or tube of regenerated cellulose in which the softening agent consists in whole or in part of a water soluble hydrochloric acid addition product of ethanolamine. Other 20 objects of the invention will appear hereinafter.

By the term rigidity" orvits equivalent as used herein is meant that property which is the opposite of limpness; in other words, rigidity in the sense that the pellicle can be advanced in a 25 wrapping machine or similar apparatus without curling, crumpling or otherwise foulin the machine.

The term durability is used to define resistance to shock or rough handling. Thus, for ex- 3 ample, bags may be fabricated from the pellicle and filled with some standard material such as a certain weight of dried beans. and the package sealed, whereupon the durability may be measured against a known standard by dropping the 35 package under standard conditions and noting the resistance of the wrapper to breakage.

The objects of this invention can be attained, in general, by treating a regenerated cellulose pellicle, or a likewater sensitive, cellulosic pellicle with a softening agent comprising a water soluble hydrochloric acid addition product of ethanolamine. As specific examples of such compounds may be mentioned monoethanolamine hydrochloride, diethanolamine hydrochloride and triethanolamine hydrochloride. The

excess softening agent is then removed from the pellicle, and the pellicle so treated is dried.

In the manufacture of regenerated cellulose sheets or films, as forexample by the viscose 5 process, the cellulosic dispersion is formed into a sheet or film by passing the same through suitable apparatus into coagulating and/or regenerating baths from which it is finally obtained in the form of a continuous cellulosic sheet which is customarily led in a continuous manner through a series of purifying, bleaching and washing operations. Just prior to the drying operation which is also usually continuous, coordinating with the sheet forming and purification operations, the film is passed through a bath containing a softening agent in such concentration that after the excess liquid has been removed from the surface of the sheet by suitable squeeze rolls and the excess moisture removed by passage through the .drier, the final sheet can be wound up in a continuous fashion and will contain an appropriate predetermined amount of softening agent. y

The commercially available dry regenerated cellulose film contains approximately 4% to 8% moisture. Depending upon the particular uses for which the product is destined, the softening agent in the sheet or film, usually glycerol, may vary from about 8% 'to 25%, based on the combined weight of the cellulose and softening agent in the sheet.

The total amount of softener in the film is controlled primarily by the totalamount of softening agent in the treating bath; film thickness, rate of passage through the bath, temperature of the bath, etc., may also contribute thereto to a certain extent. The regenerated cellulose pellicle, when reaching the treating bath, is in a highly swollen and hydrated condition and usually the cellulose of the pellicle is associated with 300% or more of water. This highly swollen and wet pellicle, usually referred to as the gel sheet, is impregnated with the treating bath. Because of the large amount of water associated with the cellulose, it is apparent that the removal of this water during the drying operation will concentrate the softening agent with respect to the cel-' lulose content of the pellicle.

Thus it is that if a regenerated cellulose pellicle containing about 15% total softener is desired as a final product, the concentration of softener'in the treating bath will be adjusted to approximately one third that value, or about 5%. This is true when the softening agents are, like glyc-- erol and the improved agents of this invention,

substantially non-volatile and are not vaporized during the drying operation. It is obvious that if a mixed softener is used, the components of which are appreciably volatile during the drying operation, then the softener concentration of the treating bath must be increased sufiiciently to compensate for the loss thereof during the drying step.

It has now been discovered that salts of the type indicated above are extremely well suited as softening agents for water sensitive, cellulosic pellicles, that is, pellicles produced from aqueous alkaline cellulosic solutions or dispersions coagulated in an acid coagulating bath, especially those of regenerated cellulose, and that they may be used as substitutes for glycerol in this capacity. Furthermore, pellicles of regenerated cellulose softened with the materials of this invention possess desirable properties which are not found in similar pellicles in which the sole flexibilizing and softening agent is glycerol.

The following examples will illustrate the prac-- tice of the invention, but it is to be understood that they are in no way limitative of the principles of the invention. 1 I

, E'aulmpZeI -A sheet or film of gel regenerated cellulose, in

temperatures, the durability of the ous bath containing monoethanolamine hydrochloride in such concentration that the final dried product will contain about 6.3% moisture and 14% of monoethanolamine hydrochloride, based on the combined Weight of cellulose and softener in thefilm. The sheet or film is allowed to remain in contact with the bath until thoroughly impregnated, whereupon it is removed from the bath, the excess liquid drained off or removed by suitable squeeze rolls, blctters or the like, when the film can be dried in the usual manner down to the final moisture content indicated above. When tested at a relative hu midity of about 35% at 24 C., or even in relative humidities as low as 15% to 22% at ordinary film is found to be at least equal to that of a similar regenerated. cellulose film softened with about 14% glycerol.

Example II Example III A sheet or continuous film of gel regenerated cellulose such that the final dry thickness will be about 0.0009 inch is treated in the manner described in Example I, using however a treating bath having a composition capable of providing a final film containing about 6.3% moisture and 17% of triethanolamine hydrochloride. In this case, the final product will be found to have excellent flexibility in addition to good surface characteristics.

Example IV Where a highly fiexibilized sheet or film of regenerated cellulose is desired and one in which transparency will not be impaired by the softener. present, a mixture of the hydrochloric acid addition product of monoand triethanolamine may be advantageously used. For instance, the following composition may be applied in the manner described in/ xample I to a film of gel regenerated cellulose such that the final dried thickness will be about 0.0012 inch:

Per cent by weight Monoethanolamine hydrochloride 3. 5 Triethanolamine hydrochloride 2. 5 Water 94. 0

The sheet or film of gel regenerated 'cellulose treated with this bath in accordance with the procedure outlined in Example I will show physical characteristics, substantially equal to or better than those of a similar regenerated cellulose sheet treated with a softener bath containing 5% of glycerol (that is, a final film containing about 15% of glycerol). In spite of the high concentration of the ethanolamine hydrochloride, the film is transparent. It is likewise extremely fiexible and durable.

The following example illustrates one method softening a regenerated cellulose sheet with a 75.

Example V A sheet or continuous film of gel regenerated cellulose similar to that of Example I is treated in the manner described in Example I, using how ever a treating bath of the following approximate composition:

' Per cent by weight Glycerol Monoethanolamine hydrochloride 2. 5 Water 95. 0

The film obtained will contain total softener in the amount of about 15% based on the combined glycolhc weight of the cellulose and softener. This film exhibits excellent physical characteristics.

The following example illustrates the method employed when a relatively volatile cellulose softener-is admixed with an ethanolamine hydrochloride and compensation is made for loss during. the drying operation.

Example VI about 0.0009 inch is immersed in or passed through a treating bath of the following approximate composition:

Per cent by weight Monoethanolamine hydrochloride 2. 5 Ethylene glycol 3. 1 Water 94. 4

In this bath, the ratio of monoethanolamine hydrochloride to ethylene glycol is about 1:1.24.

The film is treated as described in Example I and yields a final product containing about 6.3% moisture, 7.5% monoethanolamine hydrochloride, and 7.44% of ethylene glycol. The ratio of monoethanolamine hydrochloride to ethylene glycol in the dried film is thus about 1:1, the amount of ethylene glycol having been decreased by loss during the drying operation. The dried film is subsequently provided with a surface coating which may be of any type desired.

Thus, for example, it may be providedwith a moistureproofing coating which may conveniently contain a cellulose derivative, a plasticizer, a resin or blending agent, and a moistureproofing agent, such as awax or wax-like material. The surface coating in this case serves the double purpose of providing a moistureproof product and of preventing loss by evaporation of the relatively volatile ethylene glycol. Even when tested under such drastic conditions, as described in Example I, the product is transparent, flexible and more durable than a similar film softened .with'15% glycerol alone.

Films obtained in the preceding examples are found to possess, in addition to'good transparency, flexibility and durability, improved surface characteristics. Moreover, when films softened with the softening agents of this invention are coated-with a composition comprising a cellulose derivative, said coatings are found to adhere with tenacity to the base sheet and to withstand the loosening effect of water and high degrees of relative humidity. Furthermore, films softened with materials of the instant invention resist the propagation of, flames much more readily than similar films softened with glycerol.

',It is obvious that in the above examples the concentration of total softening agent in the treating bath may be suitably varied according being .tubes, such as may be obtained by the coagulatlon and/or regeneration from an aqueous cellulosic .dispersion in, accordance with the procedure customary in the art. Thus, the invention comprehends the use of regenerated cellulose pellicles such as may be obtained from the viscose or cuprammonium processes, as well as pellicles composed of glycol cellulose, cellulose acid, lowly esterified or lowly etherified cellulose derivatives where there is only one ether or ester group associatedwith several cellulose units, and other cellulosic structures of similar character.

Similarly, various types of paper, especially of the glassine type, may be used as base materials. As a matter of convenience, the invention has been described in terms of its application to the softening of regenerated cellulose pellicles such 'as those sheets or films of regenerated cellulose which are suitable for use as wrapping tissue, it understood that the scope of the invention includes any of the other bases set forth above and that the invention is equally applicable thereto.

All of the examples given in terms of 'a sheet or film of gel regenerated cellulose (gel regenerated cellulose being defined as a water swollen regenerated cellulose which has never been dried; hence that product which is obtained from the wet end of the-casting machine). Obviously, this is the more practical .way of practicing the invention since the softening agent is customarily incorporated into the sheet or film while the and during the normal course of manufacture.

- Obviously, if one desires to impregnate an already. dried regenerated cellulose film with a softener of the character described, it is possible to rewet the dried film so as to render it highly swollen, whereupon it may be treated with treating baths similar to those described, but of composition suitable for obtaining the final product desired. In the same'way, any of the sheets set forth as equivalent to regenerated cellulose sheets can be substituted in the specific examples.

The invention has been described in part in terms of the usegof glycerol in combination with the softeners of he invention. It is to be understood that other similar known cellulose softeners may be substituted for the glycerol and among those may be mentioned ethyleneglycol, diethylene glycol, triethylene glycol, carbamide, and other substances known to the art as softeners for water sensitive cellulose structures. V 4

It is also to be understood that various mixtures .of the newly described softening agents may be employed with singlesofteners of the prior art or with mixtures of the latter, de-

have been set forth formamide,

latter is in the gel .state pending upon the .type of final film desired and the purposes for which the film is to be used.

If a colored cellulosic pellicle is desired, it may be obtained in any of the ways commonly known in the art, including the passage of the sheet softening agents of the present invention are I comprising'cellulose derivatives.

sitions applied to the surface of these films adnot.

substantially solid substances at ordinary temperatures, the control of concentrations used for treating baths is greatly simplified. Because of their crystalline nature, the softening agents are available in highlypurified condition and con-.

sequently improve the quality of the final prod- However, unlike many crystalline compounds, they do not crystallize after incorporation in the sheet in the concentrations useful for softening. -They can be obtained synthetically at a very low cost in comparison to the cost of known softeners and they are available in unlimited quantity independent of a by-product source.

The use of the newly described softening agents results in a product having improved physical characteristics, particularly improved transparency, flexibility, durability, surface slip and the like. Furthermore, films softened with the materials of this invention are particularly well suited for coatings especially with compositions Such compohere with tenacity when subjected to water and high relative humidities.

ture and spirit of the invention, it is to be un-' derstood that the invention is not to be limited thereto except as set forth in the following claims.

I claim:

1. A flexible, durable, water sensitive, water insoluble cellulosic structure of the type precipitated from aqueous alkaline cellulosic solutions, said structure containing, as a softener therefor, a water soluble hydrochloric acid addition product of an ethanolamine.

2. A flexible, durable, regenerated cellulosic structure, said structure containing, as a softener therefor, a water soluble hydrochloric acid addition product of an ethanolamine.

3. A flexible, durable, water sensitive, water insoluble cellulosic structure of the type precipitated from aqueous alkaline cellulosic solutions, said structure containing, as a softener therefor, monoethanolamine hydrochloride.

4. A flexible, durable, water sensitive cellulosic structure, said structure containing, as a softener therefor, diethanolamine hydrochloride.

5. A flexible, durable, water sensitive, water insoluble cellulosic structur of thetype precipitated from aqueous alkaline cellulosic solutions, said structure containing, as a softener therefor, triethanolamine hydrochloride.

6. Regenerated cellulose softened with monoethanolamine hydrochloride.

7. Regenerated cellulose softened with diethanolamine hydrochloride. 3

8. Regenerated cellulose softened with triethanolamine hydrochloride.

9. Regenerated cellulose softened with 8% to 25% of the hydrochlorideof material having the formula:

HO-CHzCH N/ wherein X is a member of the group consisting of hydrogen and CH2CH2OH and Y is a member of the group consisting of hydrogen and FRANKLIN mavrss PETERS. 

